Seabird populations have dropped by two-thirds in the past 60 years, and may have dropped significantly even before that.

Recent studies suggest that the winged wonders that soar over the oceans are dramatically fewer than they were long ago

Many of the seabirds around the Hawaiian Islands lay their eggs and raise their young on the islands.

Some islands, notably the ones in the Northwestern Hawaiian Island archipelago, are still dense with nesting birds. Around the Main Hawaiian Islands, not so much.

But they once were nesting in massive colonies here, as well, said Storrs Olson, the famed paleoornithologist at Smithsonian Institution. Olson said bird flocks flying out to sea from those colonies would have been so dense that any early voyagers would have easily found the Hawaiian Islands if they’d gotten within a few hundred miles.

But most of those Main Hawaiian Island colonies have been lost to habitat destruction and predation.

In modern times, the decline in bird populations continues.

Researchers from the University of British Columbia reported that during the last 60 years, monitored populations of seabirds have declined 70 percent. Their work was published in the journal PLOS One. Here is Eurekalert’s printing of the university’s press release. Here's Science Daily's version.

They didn’t look at all seabirds—not all seabirds are being monitored--but their work represented studies of 500 populations worldwide, which represent 19 percent of all seabirds.

Lead author Michelle Paleczny, a UBC master's student and researcher with the Sea Around Us project, said overall populations had dropped 69.6 per cent in the 60-year period from 1950 to 2010, equivalent to a loss of about 230 million birds.

re observed in families containing wide-ranging pelagic species, suggesting that pan-global populations may be more at risk than shorter-ranging coastal populations,” the authors wrote. Those pan-pelagic species would include birds like albatrosses.

We are losing the birds to a variety of threats. The authors cite entanglement in fishing gear, overfishing of food sources, climate change, pollution, disturbance, direct exploitation, development, energy production, and introduced species like cats, dogs and other predators on nesting sites that once lacked these predators.

These are familiar stories in Hawai`i, where we regularly see stories of nesting seabirds like shearwaters, albatross and petrels being attacked on their nests by pigs, rats, cats and dogs.

The health of seabird populations is important because, as wide-ranging species, they can open a window to the health of the oceans.

“Seabird population changes are good indicators of long-term and large-scale change in marine ecosystems because seabird populations are relatively well-monitored, their ecology allows them to integrate long-term and large-scale signals (they are long-lived, wide-ranging and forage at high trophic levels), and their populations are strongly influenced by threats to marine and coastal ecosystems,” the authors wrote.